Trump Backed Off Putin Because ‘What Do You Do? End Up in a Fistfight?’

Mr. Trump reiterated his denial that his campaign had colluded with the Russians, saying it was a media witch hunt abetted by the Democrats, who he said had overplayed their hand. “When they say ‘treason,’ you know what treason is? That’s Julius and Ethel Rosenberg for giving the atomic bomb, O.K.?”

Even by Mr. Trump’s freewheeling standards, his comments were unguarded. They came during an impromptu visit to the press cabin about 90 minutes after Air Force One took off from Joint Base Andrews in Maryland on Wednesday. The White House initially put the session off the record, but then released excerpts from Mr. Trump’s remarks on Thursday after he asked why reporters had not published his statements.

In buoyant spirits despite one of his most bruising weeks as president, Mr. Trump ranged across domestic and foreign issues during the 60-minute session, from China and North Korea to immigration, health care and tax policy. But it was on Russia, which has all but consumed his White House in recent days, that Mr. Trump’s remarks were most revealing.

The president defended Mr. Putin when a reporter asked him to respond to Mr. Putin’s assertion, at a news conference, that Mr. Trump had accepted his denial of Russian involvement.

Mr. Trump again raised the prospect that countries other than Russia could have carried out the hacking, although four United States intelligence agencies concluded that Russia was solely responsible.

China and North Korea are also skilled at hacking, he said, pointing out that the North Koreans had infiltrated the internal computers of Sony Pictures. “I’m not saying it wasn’t Russia,” Mr. Trump said. “What I’m saying is that we have to protect ourselves no matter who it is.”

“Whether it’s Russia or anybody else,” he added, “we can’t let there be even a scintilla of doubt when it comes to an election.”

Mr. Trump also expressed sympathy for China’s unwillingness to do more to pressure North Korea to curb its nuclear and ballistic missile programs. China, he said, had been locked in conflict with its neighbor for “many, many centuries.” President Xi Jinping does not want “50 million people pouring across his border” from a collapsed North Korea. (The C.I.A. estimates North Korea’s population is about 25 million.)

“I understand the other side,” he said. “You always have to understand the other side.” He said of Mr. Xi, “I have a very good relationship with him. I think he’s a tremendous guy. But don’t forget. He’s for China. I’m for the U.S.”

Still, Mr. Trump said trade would give the United States leverage to pressure China to lean harder on its rogue neighbor. He said he was contemplating tariffs and quotas on Chinese steel, which he said was being dumped in the American market.

He also noted that the United States had begun renegotiating a trade agreement with South Korea, which he described as a “bad deal” and a “Hillary Clinton beauty.” President George W. Bush originally negotiated the South Korea trade deal in 2007.

Turning to immigration, Mr. Trump said he had not been joking when he said recently that a wall on the Mexican border would pay for itself if it had solar panels.

He also said the wall would have to be transparent, using an offbeat example to explain why.

“When they throw large sacks of drugs over, and if you have people on the other side of the wall, you don’t see them — they hit you on the head with 60 pounds of stuff? It’s over,” he said. “As crazy as that sounds, you need transparency through that wall.”